SU913169A1 - Method of determination of assymmetrical dispersed particle electrical characteristics - Google Patents

Description

The invention relates to a technique for determining the electrical characteristics of dispersed particles, widely used in scientific research to characterize and study the physical properties of dispersed particles, in particular bacterial cells.

There is a method of determining the electrical characteristics of asymmetric dispersed particles, which consists in registering the degree of their electrical orientation in a uniform alternating electric field by placing a suspension of the particles under study on the path of the luminous flux, imposing on it a uniform electric field of a fixed frequency, whose lines of force are directed across the direction of the luminous flux and controlling the change in the optical density of the suspension.

However, this method is not characterized by high enough sensitivity required for reliability.

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registration and accurate measurement of the degree of orientation of particles with a small amount of electric polarization, especially in the high-frequency region, due to the low signal-to-noise ratio

The closest in technical essence to the invention is a method for determining the electrical characteristics of asymmetric dispersed particles, which consists in registering the degree of their electrical orientation in a non-uniform alternating electric field by placing a suspension of the studied particles on the path of the light flux, laying a non-uniform non-uniform electric field on it, the power lines of which are directed along the direction of the light flux and monitoring the change in the optical density of the suspension when turning on la.

This method is also characterized by an insufficiently high sensitivity.

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the accuracy and accuracy of measuring the degree of electrical orientation of particles at their low concentration in suspension, at their small polarizability, small asymmetry of their shape and small size, especially in the high frequency range, where the value of electric polarizability is small.

The aim of the invention is to increase the sensitivity and accuracy of measurements when determining the electrical characteristics of asymmetric dispersed particles.

This goal is achieved by the fact that, according to the method of determining the electrical characteristics of asymmetric dispersed particles, which consists in registering the degree of their electrical orientation in a non-uniform alternating electric field by placing a suspension of the particles under study in a light beam path, applying a fixed frequency to the non-uniform electric field which are directed along the direction of the light flux, and measuring the optical density of the suspension, the suspension under study is additionally placed in the path of another luminous flux, impose on it a non-uniform field of the same frequency, the lines of force of which are orthogonal to the direction of the luminous flux, measure the optical density of the suspension in both fields, compare the measured optical density of the suspension and determine the orientation of asymmetric dispersed particles, judged by their electrical characteristics.

FIG. 1 shows a block diagram of a device implementing this method; in fig. 2 - measuring cell, general view; in fig. 3 ~ section A-A in FIG. 2; in fig. 4 shows a section BB in FIG. 3; in fig. 5 ~ frequency dependence of the degree of electro-orientation of bacterial cells, their orientation spectrum obtained at cell 3; in fig. 6 — orientation spectrum obtained on cell 2 ·; in fig. 7 "resultant orientation spectrum obtained using both cells.

The device contains a two-beam photometric system ^ consisting of a light source 1, measuring cells 2 and 3, photodetectors 4 and 5,

four

alternating voltage generator

6, a serially connected comparison unit 7, an amplifier 8 and a recorder 9. The outputs of the photodetectors 4 and 5

5 are connected to the inputs of the comparison unit

7. The measuring cells® consist (see FIGS. 2-4) of the housing 10, made of a dielectric material, electrodes 11, fittings 12 and optical

10 windows 13. Platinum electrodes are made in the form of a series of parallel conductors located at equal distances from each other. In the same cell are connected and connected to different

15 poles of the generator are conductors located in planes parallel to the direction of the light flux (longitudinal connection of electrodes), and the other is conductors located

20 in planes perpendicular to the direction of the light flux (transverse connection of the electrodes).

The registration process is carried out ₂₅ as follows.

Light from a source of 1 in. in the form of two

identical light fluxes (shown by arrows) enters the measuring cell nye 2 and 3 filled with ₃₀ cyc Penzov investigated particles. The light fluxes that pass through cells 2 and 3 are converted by photoreceivers 4 and 5 into electrical signals * which are a measure of the optical density of the suspension contained in the cells. Signals from

³⁵ photodetectors enter the comparison unit 7, where they are compared, then the resulting signal is amplified by an amplifier 8 and recorded by a recorder 9. When the generator is off

⁴⁰ 6 the field in cells 2 and 3 is absent and the particles have a chaotic orientation, and the suspensions have equal optical densities, which is ensured by equal volumes and thickness of the cells. Then

⁴⁵ include a generator 6, while in cells 2 and 3 an alternating non-uniform electric field is established _? under the influence of which the particles depending on the frequency butts ⁵⁰ Vai fields oriented either along or transverse to the field force lines and, accordingly, either along or across the direction of the light flux. If the particles are oriented in the field

⁵⁵ long axis along the field lines of force then in cell 3 with the transverse connection of the electrodes, the particles are oriented along the field under the action of the field

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of the luminous flux, which leads to an increase in the loss of light energy to the scattering of light, and consequently, an increase in the optical density of the suspension. The maximum effect is achieved when using a non-uniform electric field in the measuring cell. At the same time in the cell 2 with the longitudinal connection of the electrodes, the electric field orients the particles across the light flux, which leads to a decrease in the optical density of the suspension in cell 2.

When the particles are oriented across the field lines of force (which occurs in some cases in the high frequency range? The opposite result is observed: the optical density of the suspension in cell 3 decreases and increases in cell 2. As a result, in both cases, the output of the comparator unit 7, which subtracts signal from the photodetector 5, we get twice as much signal as when using a single measuring cell. At the same time, there is a significant reduction in the effect of noise due to fluctuations in the intensity of the light source, they go to the comparison unit with the same sign, where they are subtracted. Useful signals come to the comparison unit, having different signs, and, therefore, are added during subtraction. The size of the useful signal characterizes the degree of particle orientation in the field: the larger the signal, the higher the degree orientation.The sign of the resulting signal characterizes the direction of the orientation of the particles in the field.When subtracting a signal from the photodetector 4 from the signal from the photoreceiver 5, an increase in the resulting signal when the field is turned on is characterized by a longitudinal the decrease is the transverse orientation of the particles relative to the field lines of force. As the number of conductors that make up the electrodes increases in the direction along or across the luminous flux, the volume of the suspension and the number of particles contributing to the useful signal increase, and, consequently, the sensitivity of measurements increases. By varying the frequency of the electric field, the frequency dependence of the degree of orientation of the particles is obtained - their orientational spectrum, which contains information about the elec-

trichesky and geometrical parameters of particles.

An example of the method. Investigate the electrical orientation of fixed bacterial cells of EzsNegίsKaco1ΐ MKE-600. The test suspension with an electrical conductivity of 2 * 1O ^ ^ ohm ^ m '^ and a pH of 7.0 at a cell concentration of 10 ^ ml' ^ is poured into measuring cells 2 and 3. Then the electric field is switched on and the change in optical density is measured in three ways.

In the first method, only the signal from the photodetector 5 is recorded, which is caused by the change in the optical density of the suspension in the cell 3 with the transverse connection of the electrodes. In the second - only the signal from the photodetector 4, due to the change in the optical density of the suspension in the cell 2 with the longitudinal connection of the electrodes. In the third method - the resulting signal, after subtracting the signal from the photodetector 4 from the signal from the photodetector 5. By changing the frequency of the electric field, the orientation spectra are obtained for all three recording methods (see Fig. 5 "7 ^. Orientation spectrum (see figure 5 received at cell 3 is characterized by a small signal in the high frequency range, the spectrum obtained at cell 2 behaves in a similar way, except that in this case the recorded signal has the opposite sign (see Fig. 6). (cm Fig. 7), obtained using both cells 2 and 3, is characterized by twice the amplitude of the effect in the entire frequency range with a much lower level of noise. In this case it is especially important in the high frequency range, where the degree of electrical orientation of the particles is small.

It should be noted that the bacterial cells of E. coli are characterized by a large asymmetry of shape and, therefore, a large effect size in the region of low and medium frequencies.

In the study of particles with a small degree of asymmetry or small size, the magnitude of the recorded effect is small over the entire frequency range and, therefore, an increase in sensitivity is necessary for reliable recording of electrical orientation not only

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at high but also at low and medium frequencies. This method achieves twice the sensitivity and several times greater measurement accuracy when registering the electrical orientation of asymmetric dispersed particles, which is especially important when studying particles with a small electrical polarizability, low shape asymmetry and small size. ten

Claims (1)

Claim The method of determining the electrical characteristics of asymmetric dispersed particles, which consists in registering the degree of their electrical orientation in a non-uniform alternating electric field by placing a suspension of the particles under study on the path of the light flux, superimposing a non-uniform electric field of fixed frequency on it, whose lines of force are directed along the light flux direction 25, and measuring the optical density of the suspension, about 8 Considering that, in order to increase the accuracy and sensitivity of the method, the test suspension is additionally placed in the path of another light flux, a non-uniform field of the same frequency is superimposed on it, the lines of force of which are orthogonal to the direction of the light flux, simultaneously measure the optical densities of the suspension in both fields, they compare the measured optical densities of the suspension and determine the degree of orientation of asymmetric dispersed particles, by which their electrical characteristics are judged.